Ambipolar organic thin-film transistors using C60/pentacene structure:: Characterization of electronic structure and device property -: art. no. 233502

We fabricated ambipolar organic thin-film transistors (OTFTs) using C-60 and pentacene. The electronic structure of the interface was investigated by using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy. The magnitude of the interface dipole and the band bendings at the interface was determined, and the complete energy level diagram for C-60 on pentacene (C-60/pentacene) was obtained. The lowered band offsets, due to the enhanced charge redistribution in C-60/pentacene relative to pentacene on C-60, are favorable for the ambipolar OTFTs. The measured field-effect mobilities were 0.017 cm(2)/V s and 0.007 cm(2)/V s for the p-channel and the n-channel operations, respectively. The threshold voltages were -2 V for the p channel and 15.6 V for the n channel, comparable to those of unipolar OTFTs using C-60 or pentacene. (c) 2005 Americian Institute of Physics.